1. Field of the Invention
The present invention relates to an oscillator holding mechanism for holding an oscillator in an oscillation motor.
2. Background Art
Oscillation motor is a device which makes an oscillator having an output section vibrate to generate a rotational movement in an elliptical pattern or the like in the output section, and transmit the power to a driven body by a frictional force between the output section and the driven body by bringing the output section into contact with the driven body. Among the oscillation motors, an ultrasonic motor is suitable for reduction in size and weight because of excellent-torque at low-revolution and excellent silence. Thus, the ultrasonic motors are used as a driving source of a movable mechanism in an auto-focusing function of camera or in a scanning electron microscope or the like which requires precise positioning.
In practice, the oscillation motor generate one natural vibration or two different natural vibrations at a predetermined frequency and a predetermined timing in the oscillator having the output section, and thereby generate the rotational movement in an elliptical pattern or the like or a reciprocating movement in the output section. For example, when a bending vibration and a longitudinal vibration are generated in the oscillator and the bending vibration and the longitudinal vibration are matched in natural frequency to each other but excited respectively at predetermined timings, the rotational movement in an elliptical pattern or the like is generated in the output section. The driven body is drove by bringing the driven body into contact with the output section, and the rotational movement of the output section is transmitted to the driven body by the frictional force therebetween.
Thus, the oscillator equipped in the oscillation motor is held by a base member or the like of the oscillation motor in a state in which a fine vibration can be generated in the oscillator. For example, in an oscillation motor unit disclosed in Japanese Patent Laid-Open No. 2010-206907 proposed by the present applicant, an oscillator is held in an oscillator holder that is provided independent from a base member. The oscillator holder disclosed in Japanese Patent Laid-Open No. 2010-206907 is composed of a frame body that accommodates the oscillator in a groove-like accommodating section formed such that a protrusion for transmitting the vibration of the oscillator and an opposing side surface are exposed from the oscillator holder.
Japanese Patent Published No. 4182588 also discloses a configuration in which an oscillator is held between two opposing protrusions provided by bending a portion of a base member at 90 degrees. In practice, a support member having a square U shape in longitudinal section, the oscillator and a backlash-eliminating spring are arranged in this order between the two opposing protrusions. The oscillator is held in contact with the support member by a spring force generated by the backlash-eliminating spring. Further, Japanese Patent Laid-Open No. 2008-178250 discloses a configuration in which a guide pin is inserted into a groove formed in a holder for holding an ultrasonic oscillator of an ultrasonic motor, to restrict the travel of the ultrasonic oscillator in the holder.
The vibration of the oscillator is preferable to be converted only into a predetermined movement at the output section. However, a slight movement other than the preferable movement is generated in the practical conditions. In addition, a small gap may also exist between a holding member such as the oscillator holder and the oscillator due to deviation of accuracy in finishing of components. The above matters may affect on the vibration of the oscillator, to thereby cause a fluctuation in the movement of the output section to increase power consumption due to decrease of efficiency in output transmitting.
In Japanese Patent Laid-Open No. 2010-206907 and Japanese Patent Publication No. 4182588, the above problems cannot be solved since a large area side surface among the side surfaces of the oscillator which has a flat rectangular solid shape, a rectangular plate-like shape or the like are not held and it makes reduction of vibration fluctuation during bending vibration of the oscillator hard. Next, in the oscillation motor disclosed in Japanese Patent Laid-Open No. 2008-178250, the guide pin as a holding member is arranged on the same surface where the oscillator is pressed toward a driven member, i.e. its hold only the pressing surface and a gap between the other surfaces and the holder in the holding mechanism may exist. In a method of holding the oscillator in the conventional oscillation motors, vibration fluctuation during longitudinal vibration of the oscillator cannot be reduced, i.e. the problems described above cannot be solved.
Then, an object of the present invention is to provide an oscillator holding mechanism which enables generation of a stable vibration in an oscillator by appropriately holding the oscillator in an oscillation motor, and an oscillation motor comprising the oscillator holding mechanism.